Short stature is a condition in which a person’s height is significantly below the average for their age, sex or ethnic background. This variation is, typically, more than two standard deviations below median height.
When total height is short, but all limbs are in proportion, it is referred to as Proportionate Short Stature (PSS). Where a person’s limbs are disproportionate to their height, the condition is known as disproportionate short stature.
Depending on the underlying cause of short stature, patients can experience a wide range of associated symptoms in addition to short height. These can include fatigue, weight gain, developmental delays, congenital defects or skeletal deformities, or functional problems associated with severe short stature.
Short stature can often be associated with psychological difficulties.
The causes of short stature can be hereditary or acquired. The most common cause of short stature is genetic. For example, where both parents are of below-average height, or where there is an earlier family history of short stature. Other causes include:
Skeletal dysplasias: including achondroplasia, which is characterised by short limbs, a typical-size trunk and characteristic facial features. Osteogenesis imperfecta (‘brittle bone disease) is also typically associated with short stature.
Malnutrition: one of the most common and significant causes of short stature, malnutrition affects growth in a number of ways. By reducing the number of calories available (marasmus), the body prioritises vital functions at the expense of normal growth. Protein deficiency (Kwashiorkor) can also result in growth interruption, even if caloric needs are met.
Micronutrient insufficiency can also result in impaired growth. These include Vitamin D, which can cause bone weakening as a result of poor calcium absorption, zinc deficiency, which impairs the action of Insulin-like Growth Factor-1 (IGF-1) and iodine deficiency contributing to low levels of thyroid hormones.
Hypothyroidism: thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) are both essential for normal bone growth. Low levels of both (as in hypothyroidism) reduce stimulation of the growth plates, and can also inhibit bone maturation.
Insulin sensitivity: insulin stimulates growth by promoting uptake of glucose and amino acids into cells. Where insulin activity is impaired, the body is unable to utilise these nutrients effectively.
Pituitary tumour: pituitary tumours may be non-secreting or hormone secreting. Even non-secreting tumours may compress pituitary tissue and result in the reduced production of several hormones which are key for growth, including growth hormone (GH), thyroid-stimulating hormone (TSH) and gonadotrophins (LH and FSH). Children with growth hormone deficiency have a typical growth rate of less than 4cm per year, compared to a normal range of 5-10cm per year.
Secreting tumours produce excess levels of hormones that interfere with normal growth. These include prolactin (which can inhibit the production of sex hormones, oestrogen and testosterone) and adrenocorticotropic hormone (ACTH) which results in very high levels of cortisol.
Chronic disease: particularly celiac disease and anorexia can reduce levels of Insulin-like Growth Factor 1 (IGF-1) in the body, while chronic inflammation associated with conditions like Crohn’s disease or arthritis can interfere with its function, and the function of other key hormones involved in stimulating growth. Chronic kidney disease can negatively impact growth hormone metabolism and nutrient absorption, while congenital heart disease results in a reduction in oxygen levels and increased metabolic demand, both of which contribute to short stature.
Mitochondrial disease: a group of disorders associated with dysfunction in the mitochondria, the energy-production centres of the cell. Mitochondria are responsible for producing most of the cell’s ATP (Adenosine triphosphate) which is used for energy in processes such as bone growth, cell division and protein synthesis. As such, dysfunction has a negative effect on all. In MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like Episodes) growth failure is common, often as a result of chronic energy deficiency and lactic acidosis, which disrupts normal cellular metabolism.
Non-surgical treatment options for short stature include:
Hormone therapy: where idiopathic short stature is caused by a recognised growth hormone deficiency, it may be possible to realise an increase in both growth rate and final adult height in children using growth hormone (hGH) and Insulin-like growth factor-1 (hIGF-1). Where hypothyroidism is a causal factor, replacing thyroid hormones like levothyroxine, which is crucial for normal growth and bone maturation, can restore growth patterns if begun sufficiently early on in development.
Environmental change: psychological stress or environmental deprivation can affect growth as a result of complex neuroendocrine mechanisms. Severe emotional deprivation or neglect can result in growth failure, as can abuse, and so removal from harmful environments can often result in the resumption of normal growth.
Nutrition: in cases of malabsorption, addressing caloric and vitamin or mineral deficiencies through dietary modification or supplementation can be effective.
Orthotics and prosthetics: for functional improvements in adults with short stature, orthotic devices like shoe lifts and inserts can increase height temporarily, and for discrepancy patients, temporarily equalize leg length, improve gait symmetry and reduce discomfort.
Limb lengthening offers the most effective surgical solution to short stature, although a number of lengthening techniques exist which can be completed on the femur (thigh bone) or tibia (shin bone), or both, to achieve an increase in total height. These include:
Distraction osteogenesis: the so-called Ilizarov technique. The first step of this procedure is osteotomy, the cutting of the target bone into two parts. Traditionally, an external fixator (a complex frame pinned into place incorporating wires attached to each bone section) is used to distract (separate) the bone under tension.
A similar effect can be achieved using an internal, or intramedullary, nail. Rather than relying on an external frame to achieve distraction under tension, in this case, the nail is inserted inside the intramedullary canal of the target bone. The telescopic design of the nail enables it to push, rather than pull, the two bone lengths apart, using an external remote controller.
Where the requirement to lengthen is accompanied by deformity or misalignment in the target bone, a monorail or hexapod fixator system, such as the Taylor Spatial Frame, may be used, since they allow for simultaneous adjustment in different planes.
Acute limb lengthening
This involves the introduction of a bone graft taken from elsewhere within the body between the two parts of the osteotomised bone. This is normally carried out in a single procedure, rather than the extended periods required for distraction osteogenesis. One in place, the graft is secured in place using internal fixation, including plates, screws or rods, or external fixation, such as an Ilizarov fixator or Taylor Spatial Frame.
Given the nature of the procedure, it is typically reserved for special cases and where the requirement for length increase is relatively minor. Because of the rapid nature of the length increase, acute lengthening carries a significant risk of contractures in the muscles and tendons, which may be addressed by physiotherapy.
For further inquiries or to arrange a consultation, please contact Professor Al Muderis’ office at +61 2 88829011 or book an appointment online.
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Professor Dr Munjed Al Muderis is an orthopaedic surgeon specialising in osseointegration, hip, knee and trauma surgery. He is a clinical professor at Macquarie University and The Australian School Of Advanced Medicine, a fellow of the Royal Australasian College of Surgeons and Chairman of the Osseointegration Group.